Class Web site Username: MineralogyStudents Password: spessartine

Classification of minerals According to characteristics According to characteristics  E.g. Minerals with metallic luster, Green minerals, minerals with cleavage, etc. According to crystal shape According to crystal shape  E.g. Cubic minerals. According to chemistry According to chemistry  E.g. Minerals containing Si. Why classify minerals?

Classifying minerals Dana’s Classification System Dana’s Classification Systemhttp://  Based on chemical composition and structure

Classifying minerals Biggest group of minerals: silicates Biggest group of minerals: silicates Non-silicates: Non-silicates:  Native elements  Halides  Carbonates, Nitrates, Borates  Sufates, Chromates, Molybdenates  Phosphates, Arsenates, Vanadates –“Ore minerals”:  Sulfides  Oxides/hydroxides

Today SiO 2 minerals (i.e. quartz/chalcedony) SiO 2 minerals (i.e. quartz/chalcedony) Corundum (Al 2 O 3 ) Corundum (Al 2 O 3 ) Carbonates Carbonates  Calcite, Aragonite (CaCO 3, Dolomite (CaMg(CO 3 ) 2 ), Siderite (FeCO 3 ) Halides (salts) Halides (salts)  Halite (NaCl), Fluorite (CaF 2 ) Phosphates Phosphates  Apatite Ca 5 (PO 4 ) 3 (OH,F,Cl)

Quartz (SiO 2 ) Color: Variable. Clear, purple, pink, etc. Color: Variable. Clear, purple, pink, etc. Transparency: Crystals are transparent to translucent, cryptocrystalline forms can be translucent or opaque. Transparency: Crystals are transparent to translucent, cryptocrystalline forms can be translucent or opaque. Crystal System is trigonal; 3 2. Crystal System is trigonal; 3 2. Crystal Habits: Widely variable. Look for characteristic crystal shape (hexagonal crystals with a six sided pyramid termination). Cryptocrystalline or massive forms may be botryoidal, globular, stalactitic, etc. Crystal Habits: Widely variable. Look for characteristic crystal shape (hexagonal crystals with a six sided pyramid termination). Cryptocrystalline or massive forms may be botryoidal, globular, stalactitic, etc. Cleavage: very weak in three directions rhombohedral). Cleavage: very weak in three directions rhombohedral). Fracture: conchoidal Fracture: conchoidal Hardness: 7, less in cryptocrystalline forms. Hardness: 7, less in cryptocrystalline forms. Specific Gravity: 2.65 or less if cryptocrystalline. Specific Gravity: 2.65 or less if cryptocrystalline. Streak: white. Streak: white.

Quartz SiO 2 Clear Quartz Amethyst Smoky Quartz Rose Quartz

Cryptocrystalline Quartz SiO 2 Chert/Agate/Chalcedony

Quartz (SiO 2 ) Diagnostic features Very common. Very common. Transparency: Usually more transparent than feldspar. Transparency: Usually more transparent than feldspar. To tell apart from calcite (esp. cryptocrystalline forms): No reaction with acid. To tell apart from calcite (esp. cryptocrystalline forms): No reaction with acid. Crystal Habits: Crystals have characteristic shape. Crystal Habits: Crystals have characteristic shape. Fracture: conchoidal. Usually no cleavage. Fracture: conchoidal. Usually no cleavage. Hardness: 7, less in cryptocrystalline forms. Harder than feldspar, calcite. Hardness: 7, less in cryptocrystalline forms. Harder than feldspar, calcite.

Corundum (Al 2 O 3 ) Color: Highly variable. White or colorless, blue, red, yellow, green, brown, purple, and pink; samples can have color zonation. Color: Highly variable. White or colorless, blue, red, yellow, green, brown, purple, and pink; samples can have color zonation. Luster: Vitreous to adamantine. Luster: Vitreous to adamantine. Transparency: Transparent to translucent. Transparency: Transparent to translucent. Crystal System: Trigonal; bar 3 2/m Crystal System: Trigonal; bar 3 2/m Crystal Habits: Sapphire crystals - six-sided barrel shaped. Ruby - hexagonal prisms and blades. Crystal Habits: Sapphire crystals - six-sided barrel shaped. Ruby - hexagonal prisms and blades. Cleavage: None. Cleavage: None. Fracture: Conchoidal. Fracture: Conchoidal. Hardness: 9 Hardness: 9 Specific Gravity: Approximately 4.0+ (above average for translucent minerals) Specific Gravity: Approximately 4.0+ (above average for translucent minerals) Streak: White, harder than streak plate. Streak: White, harder than streak plate.

Corundum (Al 2 O 3 )

RARE RARE Luster: Vitreous to adamantine. Luster: Vitreous to adamantine. Transparency: Transparent to translucent. Transparency: Transparent to translucent. Crystal Habits: Sapphire crystals - six-sided barrel shaped. Ruby - hexagonal prisms and blades. Crystal Habits: Sapphire crystals - six-sided barrel shaped. Ruby - hexagonal prisms and blades. Cleavage: None. Cleavage: None. Fracture: Conchoidal. Fracture: Conchoidal. Hardness: 9 (Harder than quartz) Hardness: 9 (Harder than quartz) Specific Gravity: Approximately 4.0+ (above average for translucent minerals) Specific Gravity: Approximately 4.0+ (above average for translucent minerals) Corundum (Al 2 O 3 ) Diagnostic features

SiO 2 minerals (i.e. quartz/chalcedony) SiO 2 minerals (i.e. quartz/chalcedony) Corundum (Al 2 O 3 ) Corundum (Al 2 O 3 ) Carbonates Carbonates  Calcite, Aragonite (CaCO 3, Dolomite (CaMg(CO 3 ) 2 ), Siderite (FeCO 3 ) Halides (salts) Halides (salts)  Halite (NaCl), Fluorite (CaF 2 ) Phosphates Phosphates  Apatite Ca 5 (PO 4 ) 3 (OH,F,Cl)

Carbonates Carbonates  Calcite, Aragonite (CaCO 3, Dolomite (CaMg(CO 3 ) 2 ), Siderite (FeCO 3 ) ACID CaCO 3 + 2HCl  CaCl2 + H 2 O+ CO 2 Calcite, Aragonite -> Strong reaction to cold acid Calcite, Aragonite -> Strong reaction to cold acid Dolomite, Siderite -> Weak reaction to acid Dolomite, Siderite -> Weak reaction to acid

Calcite (CaCO 3 ) Color: extremely variable but generally white or colorless or with light shades of yellow, orange, blue, pink, red, brown, green, black and gray. Color: extremely variable but generally white or colorless or with light shades of yellow, orange, blue, pink, red, brown, green, black and gray. Luster: Vitreous to resinous to dull in massive forms. Luster: Vitreous to resinous to dull in massive forms. Transparency: Crystals are transparent to translucent. Transparency: Crystals are transparent to translucent. Crystal System: Trigonal; bar 3 2/m Crystal System: Trigonal; bar 3 2/m Crystal Habits: See web site for many crystalline forms. Also massive, fibrous, concretionary, stalactitic, nodular, oolitic, stellate, dendritic, granular, layered, etc. etc. Crystal Habits: See web site for many crystalline forms. Also massive, fibrous, concretionary, stalactitic, nodular, oolitic, stellate, dendritic, granular, layered, etc. etc. Cleavage: Perfect in three directions, forming rhombohedrons. Cleavage: Perfect in three directions, forming rhombohedrons. Hardness is 3 (only on the basal pinacoidal faces, calcite has a hardness of less than 2.5 and can be scratched by a fingernail). Hardness is 3 (only on the basal pinacoidal faces, calcite has a hardness of less than 2.5 and can be scratched by a fingernail). Specific Gravity is approximately 2.7 (average) Specific Gravity is approximately 2.7 (average) Streak is white. Streak is white. Reacts vigorously with acid. Reacts vigorously with acid.

Calcite (CaCO 3 ) Diagnostic features Very common Very common Reacts vigorously with acid. Reacts vigorously with acid. Cleavage: Perfect in three directions, forming rhombohedrons. Cleavage: Perfect in three directions, forming rhombohedrons. Hardness: 3 (soft) Hardness: 3 (soft)

Calcite (CaCO 3 )

Aragonite (CaCO 3 ) Color: White or colorless or with usually subdued shades of red, yellow, orange, brown, green and even blue. Color: White or colorless or with usually subdued shades of red, yellow, orange, brown, green and even blue. Luster: Vitreous to dull. Luster: Vitreous to dull. Transparency: Crystals are transparent to translucent. Transparency: Crystals are transparent to translucent. Crystal System: Orthorhombic; 2/m 2/m 2/m Crystal System: Orthorhombic; 2/m 2/m 2/m Crystal Habits: Hexagonal, often thin elongated prismatic, curved bladed, steep pyramidal (spiked) and chisel shaped crystals. Can also be compact, granular, radially fibrous and massive. Its massive forms can be layered, coralloid, pisolitic, oolitic, globular, stalachtitic and encrusting. The shells of many species are made up of aragonite. Crystal Habits: Hexagonal, often thin elongated prismatic, curved bladed, steep pyramidal (spiked) and chisel shaped crystals. Can also be compact, granular, radially fibrous and massive. Its massive forms can be layered, coralloid, pisolitic, oolitic, globular, stalachtitic and encrusting. The shells of many species are made up of aragonite. Cleavage: Distinct in one direction (pinacoidal). Cleavage: Distinct in one direction (pinacoidal). Hardness: (harder than calcite) Hardness: (harder than calcite) Specific Gravity: 2.9+ (average for non-metallic minerals) Specific Gravity: 2.9+ (average for non-metallic minerals) Streak: is white. Streak: is white. Reacts vigorously with acid. Reacts vigorously with acid. Best Field Indicators are crystal habits, single plane of cleavage and reaction to acid. Best Field Indicators are crystal habits, single plane of cleavage and reaction to acid.

Aragonite (CaCO 3 ) Diagnostic features Reacts vigorously with acid. Reacts vigorously with acid. Color: White or colorless or with usually subdued shades of red, yellow, orange, brown, green and even blue. Color: White or colorless or with usually subdued shades of red, yellow, orange, brown, green and even blue. Crystal Habits: Easily confused with calcite, and is often replaced by it in nature. Look for acicular or fibrous habits. Also, coral skeletons, shells, tests, etc. are deposited as aragonite (though they may later be altered to calcite). Massive forms may be indistinguishable from calcite. Crystal Habits: Easily confused with calcite, and is often replaced by it in nature. Look for acicular or fibrous habits. Also, coral skeletons, shells, tests, etc. are deposited as aragonite (though they may later be altered to calcite). Massive forms may be indistinguishable from calcite. Cleavage: Distinct in one direction (pinacoidal). Calcite cleaves in three directions. Cleavage: Distinct in one direction (pinacoidal). Calcite cleaves in three directions. Hardness: (harder than calcite) Hardness: (harder than calcite)

Aragonite (CaCO 3 )

Dolomite (CaMg(CO 3 ) 2 ) Color: Pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the crystal. Color: Pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the crystal. Luster: pearly to vitreous to dull. Luster: pearly to vitreous to dull. Transparency: crystals are transparent to translucent. Transparency: crystals are transparent to translucent. Crystal System: trigonal; bar 3 Crystal System: trigonal; bar 3 Crystal Habits: saddle shaped rhombohedral twins and simple rhombs some with slightly curved faces, also prismatic, massive, granular and rock forming. Never found in scalenohedrons. Crystal Habits: saddle shaped rhombohedral twins and simple rhombs some with slightly curved faces, also prismatic, massive, granular and rock forming. Never found in scalenohedrons. Cleavage: perfect in three directions forming rhombohedrons. Cleavage: perfect in three directions forming rhombohedrons. Fracture: conchoidal. Fracture: conchoidal. Hardness: Hardness: Specific Gravity: 2.86 Specific Gravity: 2.86 Streak: white. Streak: white. Reacts weakly with acid. Reacts weakly with acid.

Dolomite (CaMg(CO 3 ) 2 ) Diagnostic features Reacts weakly with acid. Use this test to differentiate it from Calcite and Aragonite. Reacts weakly with acid. Use this test to differentiate it from Calcite and Aragonite. Color: often pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the crystal. Color: often pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the crystal. Luster: pearly to vitreous to dull. Luster: pearly to vitreous to dull. Crystal Habits: Most commonly massive, looks very much like calcite. Crystal Habits: Most commonly massive, looks very much like calcite. Cleavage: perfect in three directions forming rhombohedrons (just like calcite). Cleavage: perfect in three directions forming rhombohedrons (just like calcite). Fracture: conchoidal. Fracture: conchoidal. Hardness: (harder than calcite) Hardness: (harder than calcite)

Dolomite (CaMg(CO 3 ) 2 )

Siderite (FeCO 3 ) Color: Yellowish brown, brown, gray, yellowish gray, or greenish gray. Color: Yellowish brown, brown, gray, yellowish gray, or greenish gray. Luster: Vitreous to pearly Luster: Vitreous to pearly Transparency: Translucent to subtranslucent Transparency: Translucent to subtranslucent Crystal System: Trigonal; bar 3 2/m Crystal System: Trigonal; bar 3 2/m Crystal Habits: Tabular, massive, botryoidal are found. Crystal Habits: Tabular, massive, botryoidal are found. Cleavage: perfect in three directions forming rhombohedrons. Cleavage: perfect in three directions forming rhombohedrons. Fracture: Conchoidal. Very brittle fracture producing small, conchoidal fragments Fracture: Conchoidal. Very brittle fracture producing small, conchoidal fragments Hardness: 3.5 Hardness: 3.5 Specific Gravity: 3.96 (denser than calcite and dolomite) Specific Gravity: 3.96 (denser than calcite and dolomite) Streak: white. Streak: white. Reacts weakly with acid. Reacts weakly with acid.

Siderite (FeCO 3 ) Diagnostic features Reacts weakly with acid (like dolomite) Reacts weakly with acid (like dolomite) Specific Gravity: 3.96 (use this to distinguish siderite from dolomite) Specific Gravity: 3.96 (use this to distinguish siderite from dolomite) Color: Variable – Yellowish, brown, grey. Color: Variable – Yellowish, brown, grey. Crystal Habits: Most commonly massive, looks very much like calcite. Crystal Habits: Most commonly massive, looks very much like calcite. Cleavage: perfect in three directions forming rhombohedrons (like calcite). Cleavage: perfect in three directions forming rhombohedrons (like calcite). Fracture: conchoidal. Fracture: conchoidal. Hardness: 3.5 (harder than calcite) Hardness: 3.5 (harder than calcite)

Siderite (FeCO 3 )

SiO 2 minerals (i.e. quartz/chalcedony) SiO 2 minerals (i.e. quartz/chalcedony) Corundum (Al 2 O 3 ) Corundum (Al 2 O 3 ) Carbonates Carbonates  Calcite, Aragonite (CaCO 3, Dolomite (CaMg(CO 3 ) 2 ), Siderite (FeCO 3 ) Halides (salts) Halides (salts)  Halite (NaCl), Fluorite (CaF 2 ) Phosphates Phosphates  Apatite Ca 5 (PO 4 ) 3 (OH,F,Cl)

Halite (NaCl) Color: Clear or white but sometimes blue, purple, pink, yellow and gray. Color: Clear or white but sometimes blue, purple, pink, yellow and gray. Luster: Vitreous. Luster: Vitreous. Transparency: Transparent to translucent. Transparency: Transparent to translucent. Crystal System: Isometric; 4/m bar 3 2/m Crystal System: Isometric; 4/m bar 3 2/m Crystal Habits: Predominantly cubes and in massive sedimentary beds, but granular, fibrous and compact forms exist. Some crystals show a crystal type called a hopper crystal. Crystal Habits: Predominantly cubes and in massive sedimentary beds, but granular, fibrous and compact forms exist. Some crystals show a crystal type called a hopper crystal. Cleavage: Perfect in three directions forming cubes. Cleavage: Perfect in three directions forming cubes. Fracture is conchoidal. Fracture is conchoidal. Hardness: 2 (softer than calcite) Hardness: 2 (softer than calcite) Specific Gravity: 2.1+ (light) Specific Gravity: 2.1+ (light) Streak:White. Streak:White. Taste: Salty Taste: Salty

Halite (NaCl) Diagnostic features Taste: Salty Taste: Salty Transparency: Transparent to translucent. Transparency: Transparent to translucent. Crystal Habits: Look for cubic crystals or fragments Crystal Habits: Look for cubic crystals or fragments Cleavage: Perfect in three directions forming cubes. Cleavage: Perfect in three directions forming cubes. Fracture is conchoidal. Fracture is conchoidal. Hardness: 2 (softer than calcite) Hardness: 2 (softer than calcite) Specific Gravity: 2.1+ (light) Specific Gravity: 2.1+ (light) Streak:White. Streak:White.

Halite (NaCl)

Fluorite CaF 2 Color: Extremely variable. Can be an intense purple, blue, green or yellow; also colorless, reddish orange, pink, white and brown. A single crystal can be multi-colored. But most often purple. Color: Extremely variable. Can be an intense purple, blue, green or yellow; also colorless, reddish orange, pink, white and brown. A single crystal can be multi-colored. But most often purple. Luster: Vitreous. Luster: Vitreous. Transparency: Transparent to translucent. Transparency: Transparent to translucent. Crystal System: Isometric; 4/m bar 3 2/m Crystal System: Isometric; 4/m bar 3 2/m Crystal Habits: Very often found as crystals with free faces, in veins and geodes. Crystals are typically cubes, to a lesser extent, octahedra. Also other rarer isometric habits. Always with equant crystals; less common are crusts and botryoidal forms. Twinning also produces penetration twins that look like two cubes grown together. Crystal Habits: Very often found as crystals with free faces, in veins and geodes. Crystals are typically cubes, to a lesser extent, octahedra. Also other rarer isometric habits. Always with equant crystals; less common are crusts and botryoidal forms. Twinning also produces penetration twins that look like two cubes grown together.Twinning Cleavage: Perfect in 4 directions forming octahedrons. Cleavage: Perfect in 4 directions forming octahedrons. Fracture: Irregular and brittle. Fracture: Irregular and brittle. Hardness: 4 (Softer than quartz) Hardness: 4 (Softer than quartz) Specific Gravity: 3.1+ (average) Specific Gravity: 3.1+ (average) Streak: is white. Streak: is white.

Fluorite (CaF 2 ) Diagnostic features Color: Most often purple, but this is not a reliable diagnostic feature as color can vary widely. Color: Most often purple, but this is not a reliable diagnostic feature as color can vary widely. Transparency: Transparent to translucent. Transparency: Transparent to translucent. Crystal System: Isometric; 4/m bar 3 2/m Crystal System: Isometric; 4/m bar 3 2/m Crystal Habits: Look for cubic and octahedral crystals, but also found in other forms such as crusts and botryoidal masses. Crystal Habits: Look for cubic and octahedral crystals, but also found in other forms such as crusts and botryoidal masses. Cleavage: Perfect in 4 directions forming octahedrons. Cleavage: Perfect in 4 directions forming octahedrons. Hardness: 4 (Softer than quartz) Hardness: 4 (Softer than quartz) Differentiate from quartz – hardness Differentiate from quartz – hardness Differentiate from calcite – no acid reaction Differentiate from calcite – no acid reaction

Fluorite (CaF 2 )

SiO 2 minerals (i.e. quartz/chalcedony) SiO 2 minerals (i.e. quartz/chalcedony) Corundum (Al 2 O 3 ) Corundum (Al 2 O 3 ) Carbonates Carbonates  Calcite, Aragonite (CaCO 3, Dolomite (CaMg(CO 3 ) 2 ), Siderite (FeCO 3 ) Halides (salts) Halides (salts)  Halite (NaCl), Fluorite (CaF 2 ) Phosphates Phosphates  Apatite Ca 5 (PO 4 ) 3 (OH,F,Cl)

Apatite (Ca 5 (PO 4 ) 3 (OH,F,Cl)) Color: Typically green but also yellow, blue, reddish brown and purple. Color: Typically green but also yellow, blue, reddish brown and purple. Luster: Vitreous to greasy and gumdrop. Luster: Vitreous to greasy and gumdrop. Transparency: Transparent to translucent. Transparency: Transparent to translucent. Crystal System: Hexagonal; 6/m Crystal System: Hexagonal; 6/m Crystal Habits: Typically a hexagonal prism with the hexagonal pyramid or a pinacoid or both as a termination. Also accicular, granular, reniform and massive. A cryptocrystalline variety is called collophane and can make up a rock type called phosphorite and also can replace fossil fragments. Crystal Habits: Typically a hexagonal prism with the hexagonal pyramid or a pinacoid or both as a termination. Also accicular, granular, reniform and massive. A cryptocrystalline variety is called collophane and can make up a rock type called phosphorite and also can replace fossil fragments. Cleavage: Indistinct in one basal direction. Cleavage: Indistinct in one basal direction. Fracture: Conchoidal. Fracture: Conchoidal. Hardness: 5 (softer than quartz). Hardness: 5 (softer than quartz). Specific Gravity: Approximately (average for translucent minerals) Specific Gravity: Approximately (average for translucent minerals) Streak: White. Streak: White. Other Characteristics: An unusual "partially dissolved" look similar to the look of previously sucked on hard candy. Other Characteristics: An unusual "partially dissolved" look similar to the look of previously sucked on hard candy.

Apatite (Ca 5 (PO 4 ) 3 (OH,F,Cl)) Diagnostic features Color: Typically green but also yellow, blue, reddish brown and purple. Color: Typically green but also yellow, blue, reddish brown and purple. Luster: Vitreous to greasy and gumdrop. Luster: Vitreous to greasy and gumdrop. Transparency: Transparent to translucent. Transparency: Transparent to translucent. Crystal Habits: Usually long, hexagonal prismatic crystals. Crystal Habits: Usually long, hexagonal prismatic crystals. Cleavage: Indistinct in one basal direction. Cleavage: Indistinct in one basal direction. Fracture: Conchoidal. Fracture: Conchoidal. Hardness: 5 (softer than quartz). Hardness: 5 (softer than quartz). Other Characteristics: An unusual "partially dissolved" look similar to the look of previously sucked on hard candy. Other Characteristics: An unusual "partially dissolved" look similar to the look of previously sucked on hard candy. Differentiate from Corundum - hardness Differentiate from Corundum - hardness

Apatite (Ca 5 (PO 4 ) 3 (OH,F,Cl))